It is necessary in a wire-drawing plant or mill to crop off the leading and trailing ends of a wire being produced, and also to cut the extremely long wire produced in one run into individual descrete sections. This operation is normally done by a so-called drum-type or running shear capable of severing the wire transversely even while moving at standard production speed, which often is in the neighborhood of 50 m/sec.
This type of shear has a pair of cantilevered drums rotatable about parallel superposed horizontal axes and each formed with a helical groove. At least one of these grooves is provided with a blade. The wire is normally advanced past these drums at a slight axial spacing from their outer ends. In order to cut the wire it is deflected axially into the mating grooves of the drums so that, as the drums rotate, the wire is drawn axially inwardly to the blade and is cut through when it reaches the blade.
The deflector, as described in East German Pat. No. 215,596, is formed by a tube through which the wire passes. The upstream end of this tube is mounted via a universal joint or swivel and the downstream end is directed tangentially at the nip defined between the two drums. This downstream end is moved by appropriate mechanism to direct the wire into the mating grooves of the drums at the desired time so as to cut the wire.
The main difficulty with these arrangements, which difficulty is particularly troublesome with relatively fine wire of a diameter of less than 5.5 mm, is almost always related to feed problems at the downstream end of the guide tube and at the cutter drums. Any misfeed can result in the wire being pinched and broken. Such a break can only be cleared with the entire string shut down, so that any such misfeed is quite expensive, both regarding the lost wire and the lost production time.